Test for trace elements first

DairyNZ provides the following information on trace elements;

Cobalt

Required for production of Vitamin B12, energy metabolism in the rumen and in the cow, fibre digestion and immunity. High manganese in soil reduces cobalt uptake by plants. Therefore, as pasture is generally high in manganese it is usually low in cobalt.

Copper

Required for growth and production, animal health and immunity, reproduction and calf viability. High intake of molybdenum, sulphur and iron, which often occurs in pasture-based diets, especially in winter and spring, reduces copper uptake by the animal.

Iodine

Required for intake, energy metabolism and milk production, protein synthesis, reproduction and heat detection. Uptake of iodine by pasture can be low. Additionally, iodine is easily leached during wet weather in winter and spring. Requirements for iodine increase during cold, wet weather.

Selenium

Required for disease resistance (e.g. mastitis), placental shedding (post calving cleaning), milk production, reproduction, calf viability and immunity. There are regions that will have high selenium levels in pasture, particularly if they have been fertilised with selenium fertiliser. In such areas supplementation should be avoided. If in doubt, consult with your vet of farm consultant.

Zinc

Required for growth and production, reproduction, hoof strength and immune system. The need for zinc supplementation will vary from farm to farm. Farms using zinc in summer for facial eczema may still require zinc supplementation in the spring. Pasture analysis should determine the need for supplementation. Excess zinc intake will increase the risk of milk fever and copper deficiency and may depress appetite.